Defending the Earth from asteroids with high-powered nuclear explosions

Just over a year ago, the Chelyabinsk meteor entered Earth’s atmosphere, streaked across the southern Urals, and detonated in a fireball that was briefly brighter than the sun. In the wake of that event, governments have paid more attention to an inevitable eventual Earth-asteroid collision. While funding for asteroid detection methods has inched up for several years, the question of how we should deal with species-ending death rocks is still in the theoretical stage.

There are three proposed scenarios for dealing with such an event:

Elect Morgan Freeman as President.

Nudge the rock out of the way using small engines or explosives that apply low amounts of delta-v for a long time.

Aggressively invoke Newton’s Third Law.

Option number three is the one we’ll be discussing today, courtesy of Bong Wie, head of Iowa State University’s asteroid deflection research division. The biggest reason for focusing efforts on short-notice methods of destroying asteroids is simple: we’re not very good at seeing them coming. Asteroids aren’t very reflective, they’re often in erratic orbits, and they have a disconcerting habit of sneaking up on us and only being detected days before they pass near the Earth. The Chelyabinsk asteroid wasn’t detected until it lit up the sky.

Bong Wie’s team is working on a device that would solve the asteroid problem through the targeted application of thermonuclear weapons. He has proposed the creation of a Hypervelocity Asteroid Intercept Vehicle (HAIV). The best way to think of it is like a high-velocity ultra-dense tank shell towing a nuclear weapon attached to a camera. The idea is simple: the high-density slug punches a crater into the rock face which becomes a focusing point for the nuclear detonation arriving just milliseconds later. Using a crater to focus the blast impact increases the total energy released into the rock and gives the bomb a greater chance of altering the trajectory of the asteroid. According to Wie’s calculations, blowing an impact crater before bomb detonation increases the overall destructive power by a factor of 20.

The most important thing about the HAIV system is that it’s something we could build today, with already-extant equipment. A Delta IV Heavy is capable of boosting a two megaton HAIV into orbit, with smaller rockets used for smaller HAIV’s.

The political difficulty of avoiding death by meteor

The downside to all this, of course, is that it’s currently illegal to launch nuclear weapons into space. People tend to get jittery when words like “nuclear weapon” are used in the same sentence as “enormous, barely-controlled chemical reaction capable of seeding large swathes of the atmosphere with radioactive particles.” While you might think that the possibility of total and complete annihilation would bring humans together in search of a short-range avoidance mechanism, to date, this hasn’t happened.

Wie is optimistic about solving these problems. In theory, the entire system could be built and tested without a nuclear payload, with that step reserved for extraordinary measures (like the detection of an imminent asteroid hit). The total cost of the vehicle is estimated at $500M — not much, when the alternatives could include the deaths of tens of millions of people.

Of course, all of this work is designed to stop asteroids of relatively modest power. Should another dinosaur-killer come spinning out of the heavens, every nuke on Earth wouldn’t do much more than give it a case of the sniffles — especially if we don’t see it coming.